When environmental protection is emphasized, the computer industry is required to produce computers that have a reduced environmental impact, such as a green computer. The most standard green computer is a computer that has reduced power consumption.
The notebook PC is the best invention in the recent years. It possesses advantages of a desktop PC, such as a high-speed calculating function and an extensible function. On the other hand, it also possesses advantages not present in a desktop PC, such as a smaller volume and portability. However, a serious problem existing in the notebook PC is that the usage time of the notebook PC is limited because of the battery life. Ordinarily, the notebook PC is connected to an AC outlet when an AC source is available. However, the notebook PC needs to be powered by its battery when there is no AC source. The usage time of the notebook PC is related to the battery life. Typically, there are two methods of increasing usage time for a notebook PC; one is to increase the battery life, but this method also increases the volume and the weight of the battery. The other method is to reduce the power consumption of the CPU in the notebook PC. Such method increases the usage time of the battery life while maintaining the same battery state.
Methods that may be used to control the central processing unit (CPU) are described as follows. The first method is the SpeedStep technology developed for controlling mobile CPUs by Intel. The basic principle of this method is that a mobile CPU runs at a speed virtually identical to that of a desktop system when the notebook computer is connected to an AC outlet. When powered by a battery, the processor drops to a lower operation frequency and voltage, conserving battery life while maintaining a high level of performance. In other words, the mobile CPU runs at different speeds as appropriate for different power sources.
Another method performs a throttling function inside the CPU. In a duty cycle, the operation system can generate a policy to run the processor at less than maximum performance. This policy may run the CPU in accordance with the state of the operation system. The throttling function mechanism provides the operation system with a function of running the CPU at a special percentage of a duty cycle. In other words, the temperature of the CPU may increase if the CPU keeps running at full speed. At this time, the operation system automatically slows down the CPU to reduce the temperature of the CPU. However, the SpeedStep technology developed by Intel does not support desktop CPUs. Furthermore, the throttling function technology permits the operation system to slow down automatically the CPU when the temperature of the CPU exceeds a specified temperature while running. In other words, the main goal of this function is thermal control, not dynamically changing the performance in accordance with the requirements of the system. Dynamically changing the performance in accordance with the requirements of the computer system is therefore difficult.
Use of a desktop CPU in a notebook computer is a valid method of reducing the manufacture cost and increasing performance efficiency. Such application of desktop CPUs in notebook computes is however hindered by the high heat generation and power consumption of the desktop CPU. The SpeedStep technology described above and developed by Intel can be directly controlled by the operation system. This SpeedStep technology permits the operation system to arrange the running schedule of the CPU to reduce the power consumption in accordance with its job condition. However, desktop CPUs developed by Intel do not support this function. A desktop CPU used in a notebook PC may cause high power consumption.
A way of detecting the current and sending a warning signal to the CPU to reduce the frequency of the CPU is therefore required. Such method may reduce not only the notebook computer manufacture cost but also the desktop CPU power consumption.